John Scott Posted February 1, 2006 Share Posted February 1, 2006 FI guys and other experienced tuners can laugh, but we all find "new to us" discoveries that make our day worthwhile. I fell into the rut of going with Holley recommendation of 1# down for every 2000' etc, then never changed the jets. Don't go to the drags lately, so what I didn't know didn't hurt. I don't know why I never did this before, but doing a web search I found a density altitude calculator http://wahiduddin.net/calc/calc_hp_dp.htm and plugged in our local conditions. Die hard racers already know this, but its amazing how much a change in temperature, humidity, pressure effects the air. At our 4662 altitude, the altitude density on a 70 degree day, typicall humidity (dry) and pressure, results in a 6000'+ density altitude. Yesterday even though it was 46 degrees, altitude density was still 5500'. Bandimere Speedway at 5800 feet sees over 10000+ on summer days. Makes you really appreciate those 10 second street cars that drive to the track! Recently changed my valve stem seals on the AFRs, and jetted for 6000'. I also read less air, more timing, so bumped it a couple more to 40 degrees total. No detonation, crisp. BINGO! I could always roll on a 1st, 2nd, sometime 3rd, burnout, never had instantaneous punch to redline bouncing off the 7000 limiter. "Like being on ice" doesn't even come close to describing the responsiveness. It puts the tires up in smoke so fast there is little thrust forward. I'm checking on track tune days so I can really play with this, but still have 2+ months to go before opening day. Live it up in the Sunbelt! John Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted February 1, 2006 Share Posted February 1, 2006 Your right john, but tuning is really where it's at and it takes alot more than just timing and jetting. It goes to headers, cam timing, rocker arm ratio, spark plug gap and the like. For instance, I built my new 406 with afr heads. Old motor had dart 2's. Both 14:1 motors on alcohol, both had roller cams. Old motor went 12.58 at 112 mph, new motor went 12.33 at 114 mph. I was dissappointed. But with tuning and tuning alone, timing, plug gap, jetting, cam timing, change of rocker arm ratio, I got it down to 11.73 at 116 mph. That's .6 seconds with tuning alone! Quote Link to comment Share on other sites More sharing options...
John Scott Posted February 1, 2006 Author Share Posted February 1, 2006 Wow .6 is a big gain, especially getting into the 11s! Timing, jetting, adjusting, and then, at least around here, you get a completely different weather system and get to start over. Thats the sport of it. Changing around the hard parts, headers, cams, rockers, seems like more permanent gains, but can be a bit harder to play with for finacial reasons. I know my headers are going to stay put as are nearly everthing else. When I get the money I'll talk you out of your twin turbo...once you got it dialed in John Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted February 2, 2006 Share Posted February 2, 2006 This thread is the best argument I've seen for EFI. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted February 2, 2006 Share Posted February 2, 2006 Well, if you think EFI is the cure all, then I think your missing the point. All engines regardless of how they are fed will respond to tuning and that includes header primary size, tube length, plug gap, ignition coil (yes these too), timing. There just isn't a perfect tune that you can swap from one motor to the next unless they are built identically and even then, which is showcased in the IROC series, there's always several of the identically prepared cars that outrun the rest. I've heard alot of guys say, oh, I run 84 jets in my 750 holley and it runs faster so you should run that too, cause it works for me. His cam, heads and intake may not pull the same signal on the carb as yours does and that may be the wrong jets. EFI will compensate for altitude changes, weather changes, etc, but it is just that, means you have one of the variables correct, but not necessarily the whole engine tuned to peak performance. Watch the pro stock guys tune those 500 inch NA motors on the dyno constantly trying this and that to see what gives them the edge. You hear it all the time on TV when watching NHRA about how this team or that team really has the edge in HP and is running the big numbers. It's all about tuning and everyone has something to learn about tuning, it makes the difference between winning and loosing and the difference between a smooth effortless powerplant and one that also runs. Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted February 2, 2006 Share Posted February 2, 2006 Hardware tuning is important, it always has been. Once the engine combo that determines the basic nature of the engine is decided, fine jetting(like responding to weather, altitude) will bring out the last drop of horsepower. On a car that is daily driven, matching fuel and oxygen(which EFI is good at) is more important since mileage is a concern. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted February 2, 2006 Share Posted February 2, 2006 Yeah, John is right about EFI being the way to go for fuel management. I'm going to have to bite the bullet and learn all about that. The MS&S really looks like it would be alot of fun and the best way to go IMO. It's hard to comprehend changing headers, but it really is worthwhile. I've seen as much as a 20HP gain with different headers especially on the big inch small block and big inch big block chevys. Quote Link to comment Share on other sites More sharing options...
John Scott Posted February 2, 2006 Author Share Posted February 2, 2006 This thread is the best argument I've seen for EFI. Dan, I had to laugh with that post, and well yes and no. If you like to just get in a go, FI is perfect. Especially for a reliable daily driver. My fantasy Z car has a twin turbo FI gazzillion HP unit, but I haven't won the lottery yet. For me on a limited budget, having FI would be a compromise in power. Not buying an expesive FI system frees up more $$ for solid roller cams and rockers, nice HP carb, etc. I'm not up on FI so I don't know if they have aftermarket systems that work well with big lumpy cams. The last shoot out I read, about 1 1/2 y.a., carburetion left the FI behind in the horsepower, but FI had a more consistant dilivery. FI is superior in most situations. If you ever looked at the fuel numbers coming off the top engine masters dyno runs, they have carburetors so well dialed in they match or surpass a FI system at all rpms. Kinda' cool thinking a person acomplished that, not a computer and O2 sensor. Some guys actually enjoy diddling with jetting, timing, adjusting, pitting their expetise against the other guy. Makes the carbureted racing series more interesting. I'M not that good, so In the meantime you can laugh at me when you start your car on a cold morning and motor off, and I can believe that dollar for dollar I have more ponies under the hood. John Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted February 3, 2006 Share Posted February 3, 2006 Well, in my world, mechanical fuel injection reigns and is king of the HP world and .700+lift roller cams are the norm. And it is the "tuner" that wins the races more often than not and an O2 sensor is the last thing I'm looking for, so you are correct you have to piddle around allllloooooootttttttt. I'm not sure about big lumpy cams, but the TT EFI motor with a gazillion HP sounds really nice. I think I'll build one just for the hell of it, after all Corzette has been sending me money to buy him parts, but he never said I couldn't use them while he was gone. So, what is the concensus on EFI and big lumpy cams? I would assume that since mechanical injection works with big mondo cams that EFI would share some similarities, but I think the MAS or MAF would create problems if you have alot of intake reversion from lots of overlap. There has got to be an EFI guru here to share wisdom. Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted February 3, 2006 Share Posted February 3, 2006 Well, if you think EFI is the cure all, then I think your missing the point. Not at all. If you love tuning, and your altimate goal is a lower E.T. then stick with a carb. Don Manzo's E.T. actually went up (slightly) when he swapped out his carb for the Stealth Ram. Mt point being that things we would never notice, like changes in air density, can make a big difference in power. EFI measures air dencity, air/fuel ratio (O2), air temp, engine temp, and throttle position every second and adjusts the fuel flow rate and timing accordingly. Carbs can't do that. But EFI has the same limitations as carbs when it comes to the hardware on and in the block. EFI is not going to compensate for a poor choice of headers or a cam. And, IMHO, I don't think anybody designs an EFI system to go drag racing. That is not where the strengths of EFI show up. Therefore, I'm not surprised that a carb beats EFI in the quarter mile, or the dyno. But if I ever drove my car anywhere else... Well, you know what my choice would be. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 3, 2006 Share Posted February 3, 2006 So, what is the concensus on EFI and big lumpy cams? I would assume that since mechanical injection works with big mondo cams that EFI would share some similarities, but I think the MAS or MAF would create problems if you have alot of intake reversion from lots of overlap. There has got to be an EFI guru here to share wisdom. Our Experience at Bonneville was as follows: Four Barrel, idled at 2200rpm, made peak power around 6500-7000 (never made it to Bonneville, only ran El Mirage because it was loosing power above 6500) Triple Weber 45's, idled at 1700, made peak power at 7500, took a few records. The dyno curve looked like someone drew it on the chart with a felt-tip pen. A classic eyebrow arch. Triple TWM 45 Throttle Bodies, idled at 1700 when starting stone cold at 39 degrees F, settling down to 800rpm idle when warm, made peak power at 8250, and made 40 more HP than the Webers at that point (8250) To get the same HP from Carbs we would have needed to run Weber 55mm DCOEs, and I shudder to think what they would have idled like. The EFI had a "quirky" curve, kinda in segments, not smooth likethe Webers, but the ability to have tractability at partial throttle to modulate wheelspin at speed was important, and the EFI had far more tractability than any of the other setups. All three setups had identical engine setup, same car, we just changed the induction system and went back to the dyno to do the usual tuning to see what kind of advance each one liked, what jetting gave the best results, where the cam gave the best results, etc... Quote Link to comment Share on other sites More sharing options...
John Scott Posted February 3, 2006 Author Share Posted February 3, 2006 The TBs sound like the ticket! Quote Link to comment Share on other sites More sharing options...
John Scott Posted February 18, 2006 Author Share Posted February 18, 2006 Cool, literally, but our density altitude is @ 1152 right now, 93% of sea level. Too bad its snowing. -6F, dew point -13F, 30.09. I could be out with 93% of normal seal level horsepower. Probably even better tomorrow morning as the humidity drops and the temps to -teens. Racing season should be in the winter! Oh well, put another log on the fire. John Quote Link to comment Share on other sites More sharing options...
Corzette Posted February 18, 2006 Share Posted February 18, 2006 Well' date=' in my world, mechanical fuel injection reigns and is king of the HP world and .700+lift roller cams are the norm. And it is the "tuner" that wins the races more often than not and an O2 sensor is the last thing I'm looking for, so you are correct you have to piddle around allllloooooootttttttt. I'm not sure about big lumpy cams, but the TT EFI motor with a gazillion HP sounds really nice. I think I'll build one just for the hell of it, after all Corzette has been sending me money to buy him parts, but he never said I couldn't use them while he was gone. So, what is the concensus on EFI and big lumpy cams? I would assume that since mechanical injection works with big mondo cams that EFI would share some similarities, but I think the MAS or MAF would create problems if you have alot of intake reversion from lots of overlap. There has got to be an EFI guru here to share wisdom.[/quote'] HAHAHAHAHAHAHA..... TBONE Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted February 18, 2006 Share Posted February 18, 2006 Oh, not having fun, please send more mon. It'll make you feel better just spending it and knowing that at least somebody is having fun! Get your can back here and come play you overachiever! Quote Link to comment Share on other sites More sharing options...
Mike C Posted February 18, 2006 Share Posted February 18, 2006 Hey John, Maybe time for a snowmobile hybrid? Something that could really put down the power when density altitude is working for you! Great post BTW. Quote Link to comment Share on other sites More sharing options...
z bomb Posted February 12, 2007 Share Posted February 12, 2007 ITB ARE the ticket. The manifold injection on the later z's in my opinion do not atomize the fuel well enough compared to the su's. The ITB's would do that in my opinion, especially with modern fuel injectors. There are different parts of the Z's stock FI system that are outdated. The electronic equipment is not capable of sending the signal to the njector in adequate time, much like the 80's Chevy's feedback carbs, they constantly produced what's known as a lean-rich condition, due to the response time from the O2 sensor to the injector. Another little tip- Instead of O2 sensors has anybody used a A/F sensor, or a lambda sensor instead? One problem with 02 sensors which the Germans have addressed is the fact that as we reach towards better combustion with upgrades and so-forth, the normal 02 levels will go down due to the complete burning of the oxygen. If one doesn't know how to tap into the system and recurve the ratio, you end up working backwards and ruining the ratio. Therefore-FI works: 1:If it is tuned right electronically, 2:It atomizes fuel just as well as SUs, 3:It pulses at the right time and within a time limit from the 02 sensor 4:Only option for turbos. (on z's as far as I know) Don't forget, FI was developed on cars for meeting emmissions. Cars sufferred due to the fact they weren't carbed anymore from late 70's to mid-late 80's. Check out NELSONRACINGENGINES.com, and Big Stuff 3 EFI controls (google). Nelson uses a cam overlap of 115 degrees and puts out 1000-1500 HP. Hope this helps.... Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted February 12, 2007 Share Posted February 12, 2007 You do realize that this threas was 1 year old, right? Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted February 16, 2007 Share Posted February 16, 2007 Tune for density altitude?!? Now you are sounding like a pilot!! Density altitude affects performance to such great extends the Pilot Operating Handbook has density altitude charts and even the local airport has a digital density altitude monitor. especially at my altitude.. (5,600 ft msl) a hot 90 degree day is terrible.. almost 8,500 feet actual density altitude Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted February 17, 2007 Administrators Share Posted February 17, 2007 Yup, and we get hit three way's... less engine power, less molecules for the prop to work with, and less molecules for the wings to work with. All this makes for a huge performance difference with as little as a 10 degree shift. BTW, Congrats on your PP Cert.!!!! P.S. I'm with Juday... THIS is what EFI is all about. Quote Link to comment Share on other sites More sharing options...
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